1. Field of the Invention
The invention concerns a device for loading and unloading a sheet on a rotating drum comprising a means for stopping the drum in a determined angular position, a drawer which slides underneath the drum and which is linked mechanically, through a part of its motion, to the drum, a clamping bar which extends a generatrix of the drum and which is held by resilient means in a position called the "closed" position, enabling the gripping of an edge of the sheet and a stop which is fixed relative to the drum and which affects the clamping, opening it when the drawer is completely pulled out.
The invention therefore relates to installations in which it is necessary to feed a rotating drum with sheets of paper, films or the like, it being necessary to clamp these latter on the drum during the operation of the installation concerned. The invention has been more particularly designed for facsimile installations ensuring the reading of data and the writing of data on a document, at the transmission set and at the receiving set respectively.
2. Description of the Prior Art
The devices commonly used are manual; they require the feeding of the sheet by the operator into a clamp or the insertion of the sheet under one or two longitudinal bars which clamp it under the effect of return springs.
Semi-automatic devices which comprise a drawer on which the documents to be wound on are set in position are also known. At the time of the pushing in of the drawer, the documents are wound onto the drum by means of a system of cables and clamping bars which engage, by suitable means, on the surface of the drum. When the drawer is pulled out of the device, the system of cables and clamping bars is detached from the drum and is wound onto the surface of the drawer. Such a device is not very versatile, inasmuch as concerns different formats of sheets and documents and the winding and coupling system for the tape and cable system constitues, by its complexity, a source of faulty operation.
With a view to simplifying the mechanism, it would be useful to fix the sheet by only one edge on the drum and to ensure the holding of the sheet on the drum by pressure or guide elements. This solution, which is implemented by some manual loading and unloading devices, cannot be directly adapted to a semi-automatic loading in which a drawer is coupled mechanically to the drum, for the pulling out of the drawer would bring the drum in the reverse direction and would jam the free edge of the document against the first obstacle which it found. In a device in which the document is held by only one edge and in which an excessive moving away of the other edge from the drum is prevented by guide elements which are set round the drum at a slight distance, it seems indeed impossible to make the drum rotate in the reverse direction at the time of unloading.